Apparatus and method for preparing a hydraulic work machine for towing

ABSTRACT

An apparatus and method for preparing a hydraulic work machine for towing in response to a dead engine condition. The apparatus includes a source of hydraulic fluid, a standby pump system hydraulically connected to the source, a plurality of pilot controls adapted for electrical activation by the standby pump system, and a hydraulic brake system. The apparatus also includes a supply valve connected to the pilot controls, and at least one lift cylinder connected to the supply valve and adapted to lift an implement on the work machine. The hydraulic brake system and the lift cylinder are enabled for hydraulic control in response to activation of the standby pump system.

TECHNICAL FIELD

This invention relates generally to an apparatus and method forpreparing a hydraulic work machine for towing and, more particularly, toan apparatus and method for raising a work implement and releasing aparking brake under dead engine conditions.

BACKGROUND ART

Hydraulic work machines, in particular mobile machines such as wheelloaders, tractors, scrapers, graders, and the like, are used extensivelyto perform work functions such as altering terrain, moving material,constructing roads, lots, runways, and repairing the same. Generallythese hydraulic work machines have a power source, i.e., an engine, tomove about, and this same power source is also used to power thehydraulic systems on the machine.

Occasionally, an engine will malfunction on a machine, thus disablingthe machine from moving about, and also disabling the hydraulic systems.It is common for such a machine to use a spring applied, hydraulicpressure released brake system; that is, the brakes are always engagedby spring action until controlled hydraulic pressure to the brakesovercomes the spring force and releases the brakes. In a dead enginesituation, the brakes will be engaged. If the machine is required to betowed, some means is needed to release the brakes for towing.

Several patents exist which disclose methods for releasing brakes fortowing under dead engine conditions. For example, in U.S. Pat. No.4,195,716, Wirt discloses a brake release mechanism for vehicle towingwhich uses a manual hydraulic pump means to manually pump fluid into thebrake system and thus disengage the brakes for towing. Although thesystem disclosed by Wirt accomplishes the purpose of releasing thebrakes, some significant effort is required by a human to perform thisprocedure. What is needed is a means to release the brakes for towingwhile minimizing the human effort required.

In addition to the need to release the brakes for towing under deadengine conditions, it often occurs that a work implement is in contactwith the ground when the engine fails. In this situation, the implementwould need to be raised above the ground to prepare the machine fortowing. The hydraulic pressure required to raise an implement,particularly a heavy implement or an implement with a heavy load, wouldbe tremendous. For example, a compactor/hammer mounted on a wheel loadermay weigh in excess of 14,000 kg. Historically, an implement is raisedfor towing by either manually pumping hydraulic fluid into liftcylinders or by connecting a pump from a service vehicle to the disabledwork machine and then pumping hydraulic fluid into the lift cylinders.In either case, it is desired to enable lifting of an implement fortowing by some convenient means located within easy access to anoperator, and without requiring the manual connection of some othersystem.

The present invention is directed to overcoming one or more of theproblems as set forth above.

DISCLOSURE OF THE INVENTION

In one aspect of the present invention an apparatus for preparing ahydraulic work machine for towing in response to a dead engine conditionis disclosed. The apparatus includes a source of hydraulic fluid, astandby pump system hydraulically connected to the source, a pluralityof pilot controls adapted for electrical activation by the standby pumpsystem, and a hydraulic brake system. The apparatus also includes asupply valve connected to the pilot controls, and at least one liftcylinder connected to the supply valve and adapted to lift an implementon the work machine. The hydraulic brake system and the lift cylinderare enabled for hydraulic control in response to activation of thestandby pump system.

In another aspect of the present invention an apparatus for lifting animplement on a hydraulic work machine in response to a dead enginecondition is disclosed. The apparatus includes a source of hydraulicfluid, a standby pump system hydraulically connected to the source, anda plurality of pilot controls adapted for electrical activation by thestandby pump system. The apparatus also includes a supply valveconnected to the pilot controls, and at least one lift cylinderconnected to the supply valve and adapted to lift an implement on thework machine. The lift cylinder is enabled for hydraulic control inresponse to activation of the standby pump system.

In yet another aspect of the present invention an apparatus forreleasing a set of hydraulically actuated brakes on a hydraulic workmachine in response to a dead engine condition is disclosed. Theapparatus includes a source of hydraulic fluid, a standby pump systemhydraulically connected to the source, and a hydraulic brake system. Theapparatus also includes a sequence valve adapted to controllably deliverhydraulic fluid to the hydraulic brake system. The hydraulic brakesystem is enabled for hydraulic control in response to activation of thestandby pump system.

In yet another aspect of the present invention a method for preparing ahydraulic work machine for towing in response to a dead engine conditionis disclosed. The method includes the steps of depressing a switch toactivate a standby pump system, activating a motor in response todepressing the switch, activating a hydraulic pump in response toactivating the motor, lifting an implement as a function of the switchbeing depressed and in response to engaging a hydraulic implement liftcontrol lever, and releasing a set of brakes as a function of the switchbeing depressed and in response to engaging a brake release lever.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an apparatus as embodied foruse in one aspect of the present invention;

FIG. 2 is a diagrammatic illustration of a control panel as embodied foruse in one aspect of the present invention; and

FIG. 3 is a flow diagram illustrating a method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, and with particular reference to FIG. 1, anapparatus 100 for preparing a hydraulic work machine for towing inresponse to a dead engine condition is shown. Preferably, the hydraulicwork machine is a mobile machine, such as a wheel loader, tractor,scraper, grader, dozer, and the like. The work machine, in the preferredembodiment, has a work implement, such as a bucket, blade, scraper,compactor, or other such implement designed to perform a work function.

In the preferred embodiment, the work machine has a power source, i.e.,an engine, to provide power for the machine to move about, and toprovide power for hydraulic systems used for various purposes, such ascontrolling the work implement or operating a set of brakes on themachine.

Occasionally, the engine will malfunction, and the machine will not beable to move on its own power. In addition, a malfunction of the enginewill disable the hydraulic systems. In this situation, it may berequired to tow the machine away from the work site.

The machine must be prepared for towing by hydraulically lifting theimplement off the ground, and hydraulically disengaging the brakes.

In FIG. 1, solid lines with arrows depict hydraulic circuits, and solidlines with arrows and diagonal slashes indicate electrical circuits.

A hydraulic tank 102 located on the work machine provides a source ofhydraulic fluid for the various hydraulic systems. Preferably, thehydraulic tank 102 provides fluid during normal operation and alsoduring dead engine operation for use with the present invention.

A standby pump system 104, located on the work machine and hydraulicallyconnected to the source of hydraulic fluid, provides pressurizedhydraulic fluid to the hydraulic systems on the work machine in theevent of a dead engine condition by means described below.

The standby pump system 104, in the preferred embodiment, includes ahydraulic pump 106, a motor 108 electrically connected to the pump 106,at least one battery 109 electrically connected to the motor 108, and amanual switch 110 electrically connected to the motor 108. The switch110 is adapted to controllably activate the standby pump system 104.During activation of the switch 110, the battery 109 provides electricalpower to the motor 108, which in turn drives the pump 106. The pump 106then provides pressurized hydraulic fluid to select hydraulic systemslocated on the work machine.

In one embodiment, the battery 109 may be a single battery capable ofsupplying electrical power to the motor 108 for a desired period oftime. However, a plurality of batteries 109 may be required and used tosupply adequate electrical power.

In the preferred embodiment, the switch 110 is a spring loadedmechanism, activated only during the time it is held in an on position.For example, the switch 110 may be a push button type of switch that isengaged only when it is pushed, and is disengaged when it is released.An advantage of this type of switch is that the standby pump system 104is only activated during time periods in which an operator intentionallyholds the switch 110 in the on position. A configuration of this sortwill prevent the standby pump system 104 from being engaged longer thandesired.

In the preferred embodiment, the hydraulic systems on the work machineinclude a plurality of pilot controls 116 that are, preferably,electrohydraulic. The electrohydraulic pilot controls 116 are, in thepresent invention, adapted for electrical activation by the standby pumpsystem 104 during those periods of time in which the switch 110 isengaged.

The work machine includes a hydraulic brake system 120. Typicalhydraulic brake systems on work machines of the type used with referenceto the present invention are spring loaded and hydraulically disengaged.That is, springs maintain the brakes in an engaged mode until theactivation of hydraulic pressure overcomes the force of the springs andreleases the brakes. In a dead engine situation, there is normally nohydraulic pressure available to release the brakes. This is normallydesired to prevent the machine from moving should an engine failureoccur, or to keep the machine from moving when the engine is shut off.However, if the machine is required to be towed, it is then desired torelease the brakes by an alternate means, such as is discussed in thepresent invention.

In one embodiment of the present invention, the hydraulic brake system120 referred to is a parking brake system. However, the presentinvention could be applied equally to the main hydraulic brake system ona machine.

A sequence valve 112 is hydraulically connected to the standby pumpsystem 104 and is adapted to controllably deliver hydraulic fluid to thehydraulic brake system 120. In FIG. 1, the sequence valve 112 isdesigned to activate in response to the hydraulic pressure at a point Pbeing at least a predetermined minimum value. This allows the standbypump system 104 to create hydraulic pressure adequate to lift a workimplement before diverting hydraulic fluid to the hydraulic brake system120.

Alternatively, the present invention may be designed to operate withouta sequence valve. This embodiment would reduce the costs of the systemwith some sacrifice in the quality of operations of the invention.

A supply valve 118 hydraulically connected to the pilot controls 116provides hydraulic fluid to at least one lift cylinder 122. The supplyvalve 118 also provides for the release of hydraulic fluid from the liftcylinder 122. For example, the supply valve 118 may supply hydraulicfluid to a head end 126 of the lift cylinder 122 and release fluid froma rod end 124 of the lift cylinder 122 to enable the lift cylinder 122to lift an implement.

In the preferred embodiment, fluid is supplied to the head end 126 ofthe lift cylinder 122 by the standby pump system 104 through a checkvalve 114. The pilot controls 116, which operate the supply valve 118,are enabled hydraulically by pressure from the lift cylinder 122 via aresolver valve 128. The resolver valve 128 provides hydraulic pressurefrom either the head end 126 or the rod end 124, whichever is greater.As the pilot controls 116 operate the supply valve 118, hydraulic fluidis released from the rod end 124 of the lift cylinder 122, thus enablingfluid to enter the head end 126, which enables the lift cylinder 122 tolift the work implement.

It is assumed in the above discussion that fluid supplied to the headend 126 of the lift cylinder 122 causes the work implement to raise.

However, the present invention would function equally well if the liftcylinder 122 is configured to raise an implement by delivering hydraulicfluid to the rod end 124 instead. In addition, the present inventioncould be configured to supply hydraulic fluid to other hydraulicdevices, for example a pitch cylinder, to enable operations of otherhydraulic features on the machine.

It is common for a hydraulic work machine to have more than one liftcylinder to raise and lower an implement. For example, a typical wheelloader may have two lift cylinders, a right lift cylinder and a leftlift cylinder. It is understood that, while discussion of the presentinvention may refer to a lift cylinder in the singular sense,application of the present invention would also include any number oflift cylinders on a hydraulic work machine.

The check valve 114 is preferably located on the hydraulic output of thestandby pump system 104 to prevent hydraulic fluid from returning to thestandby pump system 104.

In the preferred embodiment, portions of the apparatus 100 shown in FIG.1 may be part of the hydraulic systems on the work machine under normaloperating conditions. For example, the electrohydraulic pilot controls116, the supply valve 118, the hydraulic brake system 120, and the liftcylinder 122 may all be part of the normal hydraulic systems on themachine. However, the above components are also adapted for use with thestandby pump system 104 when needed.

Referring to FIG. 2, a diagrammatic illustration of a control panel 200for use with one aspect of the present invention is shown. Preferably,the control panel 200 is located within easy access to an operator,e.g., within reach of an operator in the cab of the work machine. Thecontrol panel 200 includes the manual switch 110 for activation of thestandby pump system 104 and the pilot controls 116.

The control panel 200 also includes at least one hydraulic control lever202. Preferably, a hydraulic control lever 202 on the control panel 200is an implement lift control lever. However, other hydraulic controllevers could additionally be included. For example, FIG. 2 is shownhaving three hydraulic control levers 202 a,b,c. Examples of additionalcontrol levers may include an implement tilt control lever, a brakerelease override lever, steering control levers, and any number of otherhydraulic control levers as may be used on a hydraulic work machine.Additionally, the control panel 200 may include other controls andindicators used in operation of the work machine without deviating fromthe spirit of the present invention. Alternatively, the switch 110 andthe hydraulic control levers 202 may not be located on a control panel,but may be incorporated in other locations on the work machine, e.g., ona dashboard, armrest, and the like.

Referring now to FIG. 3, a method for preparing a hydraulic work machinefor towing in response to a dead engine condition is shown.

In a first control block 302, the switch 110 is pressed to activate thestandby pump system 104 and to provide power from the battery 109 to theelectrohydraulic pilot controls 116, as shown in a fourth control block308.

In a second control block 304 the motor 108 is activated in response topressing the switch 110, which in turn activates the pump 106 in a thirdcontrol block 306.

Control then proceeds to a fifth control block 310, in which theimplement is lifted as a function of the switch 110 being depressed andin response to engaging the hydraulic implement lift control lever 202.Preferably, the implement lift operation only takes place while both theswitch 110 is depressed and the implement lift control lever 202 isactivated.

In one aspect of the invention, the lift cylinder 122 performs a liftingoperation on the implement when the hydraulic system delivers hydraulicfluid to the head end 126 of the lift cylinder 122 and releaseshydraulic fluid from the rod end 124 of the lift cylinder 122.

In a sixth control block 312, the brakes are released as a function ofthe switch 110 being depressed and in response to engaging the brakerelease lever. Preferably, the brakes are released by deliveringhydraulic fluid to the hydraulic brake system 120.

INDUSTRIAL APPLICABILITY

As an example of use of the present invention, a hydraulic work machine,e.g., a wheel loader, may become disabled at a work site due to a deadengine condition. It may be desired to tow the disabled machine awayfrom the site to perform repairs at a more convenient location, and toremove the machine from the site so that another machine may continueoperations.

However, the conditions of the brakes being applied and the workimplement being lowered to the ground may impede towing. In addition,the work machine may have been operating in an environment too harsh orhostile for a human operator to exit the machine. For example, othermachines may be working at the site and it is desirable for the operatorto remain on his disabled machine.

The present invention is designed for an operator of a hydraulic workmachine that is disabled due to a dead engine condition to be able toprepare the machine for towing, i.e., lift the implement and release thebrakes, without leaving the cab of the machine.

Other aspects, objects, and features of the present invention can beobtained from a study of the drawings, the disclosure, and the appendedclaims.

What is claimed is:
 1. An apparatus for preparing a hydraulic workmachine for towing in response to a dead engine condition, comprising: asource of hydraulic fluid located on the work machine; a standby pumpsystem located on the work machine and hydraulically connected to thesource; a plurality of electrohydraulic pilot controls adapted forelectrical activation by the standby pump system; a hydraulic brakesystem located on the work machine; a supply valve hydraulicallyconnected to the pilot controls; and at least one lift cylinderhydraulically connected to the supply valve and adapted to lift animplement on the work machine; wherein the hydraulic brake system andthe at least one lift cylinder are enabled for hydraulic control inresponse to activation of the standby pump system.
 2. An apparatus, asset forth in claim 1, wherein the standby pump system includes: ahydraulic pump; a motor electrically connected to the pump; at least onebattery electrically connected to the motor; and a switch electricallyconnected to the motor and adapted to controllably activate the standbypump system.
 3. An apparatus, as set forth in claim 1, further includinga sequence valve hydraulically connected to the standby pump system andadapted to controllably deliver hydraulic fluid to the hydraulic brakesystem.
 4. An apparatus, as set forth in claim 3, wherein the sequencevalve is adapted to controllably deliver hydraulic fluid to thehydraulic brake system in response to the pressure of the hydraulicfluid from the standby pump system being at least a predeterminedminimum value.
 5. An apparatus, as set forth in claim 1, furtherincluding a resolver valve adapted to provide hydraulic pressure to thepilot controls from one of a head end and a rod end of the at least onelift cylinder.
 6. An apparatus, as set forth in claim 2, wherein theswitch is enabled in response to an operator holding the switch in an onposition, and disabled in response to the operator releasing contactwith the switch.
 7. An apparatus, as set forth in claim 2, furtherincluding a control panel located on the hydraulic work machine, thecontrol panel including the switch and at least one hydraulic controllever.
 8. An apparatus, as set forth in claim 7, wherein one of the atleast one hydraulic control lever is an implement lift control lever. 9.An apparatus, as set forth in claim 1, further including a check valvelocated on the hydraulic output of the standby pump system to preventhydraulic fluid from returning to the pump system.
 10. An apparatus forlifting an implement on a hydraulic work machine in response to a deadengine condition, comprising: a source of hydraulic fluid located on thework machine; a standby pump system located on the work machine andhydraulically connected to the source; a plurality of electrohydraulicpilot controls adapted for electrical activation by the standby pumpsystem; a supply valve hydraulically connected to the pilot controls;and at least one lift cylinder hydraulically connected to the supplyvalve and adapted to lift an implement on the work machine; wherein theat least one lift cylinder is enabled for hydraulic control in responseto activation of the standby pump system.
 11. An apparatus, as set forthin claim 10, wherein the standby pump system includes: a hydraulic pump;a motor electrically connected to the pump; at least one batteryelectrically connected to the motor; and a switch electrically connectedto the motor and adapted to controllably activate the standby pumpsystem.
 12. An apparatus, as set forth in claim 10, further including aresolver valve adapted to provide hydraulic pressure to the pilotcontrols from one of a head end and a rod end of the at least one liftcylinder.
 13. An apparatus, as set forth in claim 11, wherein the switchis enabled in response to an operator holding the switch in an onposition, and disabled in response to the operator releasing contactwith the switch.
 14. An apparatus, as set forth in claim 11, furtherincluding a control panel located on the hydraulic work machine, thecontrol panel including the switch and at least one hydraulic controllever.
 15. An apparatus, as set forth in claim 14, wherein one of the atleast one hydraulic control lever is an implement lift control lever.16. An apparatus for releasing a set of hydraulically actuated brakes ona hydraulic work machine in response to a dead engine condition,comprising: a source of hydraulic fluid located on the work machine; astandby pump system located on the work machine and hydraulicallyconnected to the source; a hydraulic brake system located on the workmachine; and a sequence valve hydraulically connected to the standbypump system and adapted to controllably deliver hydraulic fluid to thehydraulic brake system; wherein the hydraulic brake system is enabledfor hydraulic control in response to activation of the standby pumpsystem.
 17. An apparatus, as set forth in claim 16, wherein the standbypump system includes: a hydraulic pump; a motor electrically connectedto the pump; at least one battery electrically connected to the motor;and a switch electrically connected to the motor and adapted tocontrollably activate the standby pump system.
 18. An apparatus, as setforth in claim 16, wherein the sequence valve is adapted to controllablydeliver hydraulic fluid to the hydraulic brake system in response to thepressure of the hydraulic fluid from the standby pump system being atleast a predetermined minimum value.
 19. An apparatus, as set forth inclaim 17, wherein the switch is enabled in response to an operatorholding the switch in an on position, and disabled in response to theoperator releasing contact with the switch.
 20. A method for preparing ahydraulic work machine for towing in response to a dead enginecondition, including the steps of: depressing a switch to activate astandby pump system; activating a motor in response to depressing theswitch; activating a hydraulic pump in response to activating the motor;enabling a plurality of electrohydraulic pilot controls in response todepressing the switch; controllably lifting an implement as a functionof the switch being depressed and in response to engaging a hydraulicimplement lift control lever; and controllably releasing a set of brakesas a function of the switch being depressed and in response to engaginga brake release lever.
 21. A method, as set forth in claim 20, whereincontrollably lifting an implement includes the steps of: deliveringhydraulic fluid to a head end of a hydraulic lift cylinder; andreleasing hydraulic fluid from a rod end of a hydraulic lift cylinder.22. A method, as set forth in claim 20, wherein controllably releasing aset of brakes includes the step of delivering hydraulic fluid to ahydraulic brake system.